Two-cycle internal-combustion engines



March 1966 KAZUHIRO SUNOBE ETAL 3,237,397

TWO-CYCLE INTERNAL-COMBUSTION ENGINES Filed April 30, 1964 3 Sheets-Sheet 1 F/G. lb

iEflUEfiTORS HQ-Z-UHH'O umba hio nsgeshx a, m m a ATTORNEY March 1, 1966 KAZUHIRO SUNOBE ETAL 3,237,397

TWO-CYCLE INTERNAL-COMBUSTION ENGINES 3 Sheets-Sheet 2 Filed April 30, 1964 FIG: 3b

In UE HT'ORQ zuh ir-o u b ATTORNEY March 1966 KAZUHIRO SUNOBE ETAL 3,237,397

TWO-CYCLE INTERNAL-COMBUSTION ENGINES Fild April 30, 1964 3 Sheets-Sheet 5 IHVE hmRS Qzuhiro un a w 6 u H Bshio agashi y m1. (a

ATTORNEY United States Patent 3 237,397 TWO-CYCLE INTERNAL-COMBUSTION ENGINES Kazuhiro Sunobe and Toshio Nagashima, both of Tokyo,

Japan, assignors to Hitachi, Ltd., Tokyo, Japan, a corporation of Japan Filed Apr. 30, 1964, Ser. No. 363,804 Claims priority, application Japan, May 11, 1963, 38/ 24,913 8 Claims. (Cl. 60-13) This invention relates to twocycle internal-combustion engines having an exhaust gas turbo-charger.

In order to start two-cycle internal-combustion engines it is necessary to rotate the crankshaft and simultaneously to feed scavenging air into the engine cylinder or cylinders. Particularly with engines of the type employing a scavenging blower driven by an exhaust gas turbine, any self-scavenging eflfect cannot be obtained until the engine starts to operate on a regular scale as distinct from those engines in which the scavenging blower is driven directly by mechanical means. To overcome this difficulty, various procedures have previously been taken with twocycle internal-combustion engines having an exhaust gas turbo-charger. In one procedure, an independent blower is used 'to supply air for starting the engine. In another procedure, a blower means is used which is operably connected with the engine crankshaft. In a further procedure, compressed air is utilized to start the engine and the air from the cylinder is directed through the exhaust gas turbine to start it. These procedures, however, have involved the following problems. The first procedure necessitates a separate power source to drive the blower and a complicated piping arrangement. Also, an appropriate switching device is required which is operable after the starting of the engine and this makes the entire engine arrangement further complicated. The second procedure obviously makes the engine mechanism complicated and during normal engine operation part of the power generated must be consumed to drive the blower. Finally, the third procedure, requiring a separate arrangement of an air compressor, may be suitable for engines of relatively high power output but is not recommendable with small engines for automotive, construction and other uses in which the mobility of the engine forms one of the major considerations.

In view of these problems previously encountered, the present invention proposes to arrange back-flow preventing means in the exhaust pipe from the engine cylinder thereby eliminating the need of providing a separate blower means. With this arrangement, when the crankshaft is rotated in order to start the engine, the engine itself serves as a pump to drive the exhaust gas turbo-charger, as Will be described hereinafter in detail.

According to the present invention, there is provided a two-cycle internal-combustion engine having an exhaust gas turbo-charger which is characterized by the provision of a back-flow preventing means in the exhaust pipe from the engine cylinder whereby, in starting the engine, when the crankshaft is rotated, a substantial air pressure effective to drive the exhaust gas turbo-charger is formed in the cylinder.

The present invention will now be described in further detail with reference to the accompanying drawings, in which:

FIG. la is a diagrammatic illustration of a conventional two-cycle internal-combustion engine with exhaust valve means and an exhaust gas turbo-charger;

- FIG. lb is a diagrammatic illustration of a conventional port-scavenging two-cycle engine combined with an exhaust gas turbo-charger;

FIG. 2a is a diagrammatic illustration of a two-cycle internal-combustion engine with exhaust valve means and an exhaust gas turbo-charger, including a non-return valve arrangement according to the present invention;

FIG. 2b is a diagrammatic illustration of a port-scavenging two-cycle engine combined with an exhaust gas turbo-charger and having a non-return valve according to the present invention;

FIG. 3a illustrates the engine of FIG. 2a during the up stroke of the piston;

FIG. 3b illustrates the engine of FIG. 2b during the up stroke of the piston;

FIG. 4a illustrates the engine of FIG. 211 during the down stroke of the piston;

FIG. 4b illustrates the engine of FIG. 2b during the down stroke of the piston;

FIG. 5a illustrates the engine of FIG. 2a during the scavenging process;

FIG. 5b illustrates the engine of FIG. 2b during the scavenging process;

FIG. 6a illustrates the engine of FIG. 2a in its normal running state;

FIG. 6b illustrates the engine of FIG. 2b in its normal running state;

FIG. 7a illustrates the engine of FIG. 2a equipped with a vacuum limiting valve; and

FIG. 7b illustrates the engine of FIG. 2b equipped with a vacuum limiting valve.

In the following description, the principles of the present invention will be explained with reference to the accompanying drawings. Reference will first be made to FIGS. 1a and lb, which illustrate two forms of conventional two-cycle internal-combustion engines having an exhaust gas turbo-charger. With these engines, even if the crankshaft 5 is rotated in order to start the engine, the exhaust will not be directed to the turbine to start the exhaust gas turbo-charger 4. In contrast, where the internal-combustion engine has a non-return valve 1 arranged in the exhaust pipe according to the present invention, as shown in FIGS. 2a or 2b, rotation of the engine crankshaft 5 forces air out of the cylinder 7 through the exhaust gas turbine 4 to drive the latter.

FIGS. 2a, 3a, 4a, 5a, 6a and 7a diagrammatically illustrate a uniflow-scavenging two-cycle engine with exhaust valve means embodying the present invention. In order to start the engine, decompression cam 2 is first rotated to lower the exhaust valve 3 into its open position while the non-return valve 1 is held closed by spring means, as shown in FIG. 2a. Under this condition, air from the cylinder can flow to the exhaust gas turbine opening the non-return valve 1 but cannot flow in opposite direction. However, when the engine crankshaft 5 is rotated by starter motor or other means, the cylinder space above the piston 6 is reduced as it rises, as seen in FIG. 3a, and the air is forced out of the cylinder to flow past the exhaust valve 3 and non-return valve 1 and through the turbine side 4T of the exhaust gas turbocharger 4 to drive the latter. Apparently, the blower side 40 of the exhaust gas turbo-charger 4 is simultaneously driven to deliver air into the scavenging air chamber 8 of the engine. As the piston 6 passing the upper dead point descends, the non-return valve 1 is closed, as shown in FIG. 4a, preventing air from flowing into the cylinder and the air pressure therein is reduced to a vacuum. When the crankshaft 5 further rotates to assume the position shown in FIG. 5a, the scavenging air port 9 is opened to allow the scavenging air to be drawn into the cylinder. The crankshaft 5 continues to rotate and again assumes the position shown in FIG. 2a. As the above process is repeated, the exhaust gas turbocharger 4 will attain a sufficient speed of rotation to deliver air under pressure to the scavenging air chamber. At this point, the decompression cam 2 is rotated to restore the exhaust valve 3 to its normal position, as

shown in FIG. 6a. Subsequently, being fed with appropriate fuel, the engine starts to rotate by itself. During normal operation, the non-return valve 1 is useless and is held against the adjacent wall of the exhaust pipe, as shown in FIG. 6a.

Reference will next be made to FIGS. 2b, 3b, 4b, 5b, 6b and 7b, which diagrammatically illustrate a portscavenging two-cycle engine embodying the present invention.

Just as in the case of FIG. 2a, this second embodiment includes a non-return valve 1' arranged in the exhaust pipe. In addition, this embodiment includes starting decompression valve 3' arranged in the top of the cylinder 7, a conduit 10 and a decompression cam 2.. For starting the engine, the decompression cam 2' is rotated in advance to push down the starting decompression valve 3' while the non-return valve 1 is held in closed position by spring means. When the engine crankshaft 5 is driven by the starter motor, the air in the cylinder is forced out therefrom to drive the exhaust gas turbocharger 4. As illustrated in FIGS. 3b, 4b and 515, this process is just similar to that with the case of a unifiowscavenging engine described hereinbefore. After the engine has reached its normal operational state, the decompression cam 2' is restored to its normal position to close the starting decompression valve 3 while holding the non-return valve 1' against the adjacent pipe Wall, as shown in FIG. 6b.

As apparent from the foregoing description, the provision of a non-return valve in the exhaust pipe enables rotation of the exhaust gas turbo-charger in the starting operation, but, during the down stroke of the engine piston, the vacuum formed in the cylinder may possibly become excessive. In such cases, a vacuum limiting valve may desirably be employed as indicated at 11 or 11 in FIGS. 7a and 7b. In cases of two-cycle internal-com bustion engines of the multi-cylinder type, the back-flow preventing means of the invention may be arranged in the exhaust pipe from a certain cylinder or in the respective exhaust pipes from some or all of the engine cylinders.

According to the present invention, it will be appreciated that two-cycle internal-combustion engines of the type including a starter motor or other starter means to rotate the engine crank shaft can be started without necessitating any separately arranged motor-driven blower or a blower operatively connected with the crankshaft since the rotation thereof serves at all times to drive the exhaust gas turbo-charger. It will be apparent to those skilled in the art that the present invention is applicable to any form of two-cycle internal-combustion engine having an exhaust gas turbo-charger irrespective of the size of the engine and also to the spark-ignition type of twocycle engines.

What is claimed is:

1. A two-cycle internal-combustion engine having an engine cylinder, an exhaust pipe operatively connected with said cylinder, an outlet valve in said cylinder, and an exhaust gas turbo-charger fed with exhaust gases by way of said exhaust pipe, characterized by the provision of a back-flow preventing means in the exhaust pipe from the engine cylinder and decompression means for holding said outlet valve in the open position thereof during start of the engine, whereby in starting the engine when the engine crankshaft is rotated a substantial air pressure effective to drive the exhaust gas turbo-charger is formed in the cylinder.

2. A two-cycle internal combustion engine assembly, comprising:

cylinder means slidably receiving therein piston means,

exhaust gas driven turbo-charger means,

exhaust pipe means operatively connecting the cylinder means with the turbo-charger means to conduct exhaust gases to said turbo-charger means,

exhaust gas back-flow preventing means within said exhaust pipe means, and control means for maintaining, during starting operation, said piston cylinder in substantially open communication with said exhaust pipe means throughout both engine cycles. 3. A two-cycle internal combustion engine assembly, comprising:

cylinder means slidably receiving therein piston means, exhaust gas driven turbo-charger means, exhaust pipe means operatively connecting the cylinder means with the turbo-charger means to conduct exhaust gases to said turbo-charger means, exhaust gas back-flow preventing means within said exhaust pipe means, and control means for maintaining, during starting operation, said piston cylinder in substantially open communication with said exhaust pipe means throughout both engine cycles, said control means including outlet valve means and actuating means for said outlet valve means. 4. A two-cycle internal combustion engine assembly, comprising:

cylinder means slidably receiving therein piston means, exhaust gas driven turbo-charger means, exhaust pipe means operatively connecting the cylinder means with the turbo-charger means to conduct exhaust gases to said turbo-charger means, exhaust gas back-flow preventing means within said exhaust pipe means, and control means for maintaining, during starting opperation, said piston cylinder in substantially open communication with said exhaust pipe means throughout the engine cycle, and vacuum limiting valve means disposed Within said exhaust pipe means between said control means and said back-flow preventing means. 5. A two-cycle internal combustion engine assembly, comprising:

cylinder means slidably receiving therein piston means, exhaust gas driven turbo-charger means, exhaust pipe means operatively connecting the cylinder means with the turbo-charger means to conduct exhaust gases to said turbo-charger means, exhaust gas back-flow preventing means Within said exhaust pipe means, and control means for maintaining, during starting operation, said piston cylinder in substantially open communication with said exhaust pipe means throughout the engine cycle, said control means including outlet valve means and actuating means for said outlet valve means, said outlet valve means being operatively disposed between said back-flow preventing means and said cylinder means. 6. A two-cycle internal combustion engine assembly, comprising:

cylinder means slidably receiving therein piston means, exhaust gas driven turbo-charger means, exhaust pipe means operatively connecting the cylinder means with the turbo-charger means to conduct exhaust gases to said turbo-charger means, exhaust gas back-flow preventing means within said exhaust pipe means, and control means for maintaining, during starting operation, said piston cylinder in substantially open communication with said exhaust pipe means throughout the engine cycle, said control means including outlet valve means an actuating means for said outlet valve means, said outlet valve means being operatively disposed between said backflow preventing means and said cylinder means, said actuating means including a cam in operative engagement with said outlet valve.

7. A two-cycle internal combustion engine assembly, comprising:

cylinder means slidably receiving therein piston means,

exhaust gas driven turbo-charger means,

exhaust pipe means operatively connecting the cylinder means with the turbo-charger means to conduct exhaust gases to said turbo-charger means,

exhaust gas back-flow preventing means within said exhaust pipe means,

and control means for maintaining, during starting operation, said piston cylinder in substantially open communication with said exhaust pipe means throughout the engine cycle,

said control means including outlet valve means and actuating means for said outlet valve means,

said outlet valve means being operatively disposed between said back-flow preventing means and said cylinder means,

said actuating means including a cam in operative engagement with said outlet valve,

and vacuum limiting valve means disposed within said exhaust pipe means between said control means and said back-flow preventing means.

8. 111 a two-cycle internal combustion engine including a cylinder provided with an inlet port and with an exhaust port having an exhaust valve controlling the flow of engine exhaust gases therethrough, an engine exhaust gas driven turbo-charging device driven by engine exhaust gases flowing from the engine exhaust port through an exhaust pipe and supplying air to the engine inlet port,

the improvement essentially consisting of exhaust gas back-flow preventing means disposed within the exhaust pipe rearwardly of the exhaust valve and means operable to hold the exhaust valve continuously open during engine starting operation until substantial exhaust gas pressure effective to drive the turbo-charger device is built up in the piston cylinder.

References Cited by the Examiner UNITED STATES PATENTS 1,225,259 5/ 1917 Lowe.

2,097,883 1l/1937 Johansson -13 2,431,563 11/ 1947 Johansson 60-13 2,820,339 1/ 1958 Grieshaber 60-13 MARK NEWMAN, Primary Examiner.

RICHARD B. WILKINSON, Examiner. 

1. A TWO-CYCLE INTERNAL-COMBUSTION ENGINE HAVING AN ENGINE CYLINDER, AN EXHAUST PIPE OPERATIVELY CONNECTED WITH SAID CYLINDER, AN OUTLET VALVE IN SAID CYLINDER, AND AN EXHAUST GAS TURBO-CHARGER FED WITH EXHAUST GASES BY WAY OF SAID EXHAUST PIPE, CHARACTERIZED BY THE PROVISION OF A BACK-FLOW PREVENTING MEANS IN THE EXHAUST PIPE FROM OF ENGINE CYLINDER AND DECOMPRESSION MEANS FOR HOLDING SAID OUTLET VALVE IN THE OPEN POSITION THEREOF DURING START OF THE ENGINE, WHEREBY IN STARTING THE ENGINE WHEN THE 